The move they'll make (I've seen this firsthand) is they'll exclude the most senior people (architects, distinguished engineers) from union eligibility. Leadership will do this by including them in meetings where they are privy to sensitive and confidential information and then will classify them as a 'confidential employee'.

This tactic is useful in ensuring that you always have a few people who can _probably_ keep the lights on, even if they are sub-optimally practiced at those systems.